Fluidic fuel system with back pressure control

ABSTRACT

A FUEL SYSTEM HAVING FLUID LOGIC COMPONENTS IS PROVIDED WITH MEANS OF MAINTAINING FLUID BACK PRESSURE WITHIN THE FLUID LOGIC ELEMENT AT A CONSTANT LEVEL REGARDLESS OF THE ATTITUDE AND OPERATIVE SITUATION OF THE FUEL SYSTEM. A PREFERRED EMBODIMENT OF THE BACK PRESSURE MAINTAINING MEANS COMPRISES A NAROW RESERVOIR MAINTAINED BEHIND A WEIR INTO WHICH ALL FLUID EXHAUST AND VENT PASSAGES ARE CONNECTED AT AN INLET POINT BELOW THE TOP OF THE WEIR. FLUID DISCHARGE IN EXCESS OF THE RESERVOIR VOLUME SPILLS OVER THE WEIR INTO A RETURN LINE WHERE IT IS RETURNED TO THE FUEL TANK.

United States Patent O 3,567,191 F LUIDIC FUEL SYSTEM WITH BACK PRESSURECONTROL Donald F. Morgan, Horseheads, N.Y., assignor to The BendixCorporation Filed July 15, 1969, Ser. No. 841,840 Int. Cl. F02m 69/04US. Cl. 261--36 11 Claims ABSTRACT OF THE DISCLOSURE A fuel systemhaving fluid logic components is provided with means of maintainingfluid back pressure within the fluid logic element at a constant levelregardless of the attitude and operative situation of the fuel system. Apreferred embodiment of the back pressure maintaining means comprises anarrow reservoir maintained behind a weir into which all fluid exhaustand vent passages are connected at an inlet point below the top of theweir. Fluid discharge in excess of the reservoir volume spills over theweir into a return line where it is returned to the fuel tank.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to the art of fuel handling and metering for mixture with air toprovide a combustible mixture for an internal combustion engine. Morespecifically, the present invention relates to fuel systems which employfluid logic elements to control the fuel metering.

Description of the prior art A wide variety of fuel systems are wellknown in the art. Of recent appearance in the art are fuel systems whichutilize fluidic devices to partially or totally control the fuelmetering function. Examples of this art may be found in US. LettersPatent 3,386,710 issued to J. B. York, Jr., 3,389,894 issued to A. M.Binder and 3,406,951 issued to C. Marks to name a few. While the systemsdisclosed in the referenced patents utilize fluidic elements, theyshould not be thought of as complete systems since in an engineoperating cycle these systems utilize an essentially constant fuel/airratio whereas the fuel/air ratio must be varied to provide variousenriched ratios such as cold start, acceleration, wide-open throttle,and full load enrichment. All of these variously ratioed enrichedmixtures may be provided by controllably altering the control signals tothe primary computing element through additional fluid logic circuitry.However, systems that provide accurate fuel/air ratios in testssimulating all engine requirements suddenly become highly inaccuratemisapproximations when these identical systems are installed inautomobiles wherein the system is subjected to vibration and other typesof periodic and aperiodic motion.

It is a characteristic of all the known fluidic fuel systems that themain, or primary, fluidic stage comprises a nozzle dischargingpressurized fluid into a fluid interaction region where control signals,disposed laterally of the fluid stream, deflect the stream towards oneof a plurality of outlet ports. In systems where the fluid is fuel, oneoutlet port is associated with a fuel discharge nozzle in the air intakeof the engine while another outlet port permits fuel entering thereintoto be returned to the fuel tank. In such systems when installed invehicles, it has been found that accelerations and decelerations towhich the vehicle is subjected are not instantaneously transmitted tothe fuel thereby causing undesired variations in the 3,567,l9l PatentedMar. 2, 1971 fuel pressure within the fuel system. This effect is notparticularly noticeable on the fluid which is under positive pressure asat the fluid logic power nozzle. However, the effect is quite noticeableon the fuel in the return line which is unpressurized and in mostinstances must run the length of the automobile in the direction ofgreatest variations in acceleration. The vehicle descending of a gradeor a deceleration of the vehicle caused by braking will cause the fuelin the return-line to tend to travel toward the return-line inlet. Sincethis is at the fluid interaction region of the fluid logic device ordevices, this would cause a sudden increase in the pressure on that sideof the power fluid stream thereby deflecting an undesirably highquantity of fuel into the outlet port associated with the air intake ofthe internal combustion engine causing the fuel/air ratio to be higherthan that required for best engine performance.

On the other hand, vehicle acceleration would cause fuel in thereturn-line to flow away from the fluidic ele ment at a higher flow ratethan normal thereby causing a low pressure zone to form adjacent thepower stream which would be operative to divert a larger portion of thepower stream into the return line outlet passage of the fluidic elementor elements. The fuel/ air ratio would then become leaner than desired.It has, therefore, become evident that fluid logic fuel systems, atleast as applied to automotive engines, require some means formaintaining the pressure in the fluid return outlet of the fluidicportion of the system at a substantially constant value which isuneffected by vehicle attitude or acceleration. It is a primaryobjective of this invention to provide, in an automotive fuel supplysystem, a means to maintain the fluidic portion fluid return portpressure at a substantially constant value regardless of vehicleattitude and acceleration. It is a still further object of the presentinvention to provide such a device which is reliable in operation andlow in cost. It is a still further object of the present invention toprovide a device for a fluidic fuel supply system capable of insulatingthe fluid logic metering portion of the system from the effects ofacceleration and attitude upon the fuel in the fuel tank or return-line.

SUMMARY OF THE INVENTION The present invention comprises the addition ofa constant volume reservoir within the fuel return portion of a fluidicfuel system, in proximity to the fluidic computing and metering portionof the system which insulates that portion of the system from the fueltank and from a major portion of the return-line. By discharging fueldirectly into the center of this reservoir from the return-line port,and/or all vent ports of the fluidic elements, attitude effects upon thefuel return system are significantly reduced thereby stabilizing theattitude responsive component of the pressure variation at the fuel ventport in the primary metering element. Acceleration (inertial) effectsare minimized by permitting only a minimum of fluid to be retainedwithin the reservoir and by orienting the reservoir, with respect to thevehicle, so that an acceleration of the vehicle will cause minimal fluidforces to be exerted upstream of the reservoir.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows, in schematic form, a fuelsystem for a vehicle incorporating the present invention.

FIG. 2 shows the preferred embodiment of the insulating reservoir meansin a top view with the cover plate removed.

FIG. 3 shows the insulating reservoir means of FIG. 2 in a sectionalview taken along line 3--3 in FIG. 2.

FIG. 4 shows a sectional view, taken along line 44 in FIG. 5, of analternative isolating reservoir for use in the system shown in FIG. 1.

FIG. 5 shows a side view of the reservoir of FIG. 4.

DETAILED DESCRIPTION OF THE DRAWING Referring now to the schematicdiagram of FIG. 1, a representative fuel system is shown comprising afuel tank 10, a fuel pumping means 12, a fuel metering and dischargemeans 14, and insulating means 16. Conduit 18 provides fuel to the pumpinlet, conduit 20 communicates fuel under elevated pressure to the fuelmetering and discharge means 14 and return conduit 22 communicatesexcess fuel from the insulating means 16 to the fuel tank 10. Returnconduit 22 includes a check valve 24 which is operative to prevent fluidflow in the return line from reversing as might happen if the tank wereelevated above the insulating means.

For completeness, the fuel metering and discharge means 14 has beenillustrated as including a fluidic computation means illustrated asfluidic device 26 which includes a pair of outlet passages, 28 and 30, apair of control passages 32 and 34 and a power stream input passage 36which receives pressurized fuel from the fuel pump 12. Outlet passage 28is adapted to receive the controlled power fluid stream from inputpassage 36 and to communicate the fluid, which in this instance ismetered fuel, to a discharge nozzle 38 situated in the air intake 40 ofan engine, not shown. The control passage 34 of the fluid logicamplifier 26 could be, for instance, in communication with the venturi42 where it would receive as a control signal the depression at theventuri 42 which is indicative of air flow to the engine, not shown, andwhich would comprise the primary signal indicative of the engine fueldemand. Control passage 32 would be arranged to establish an operatingbias for the amplifier 26 as, for instance, by connection to a pressuresource such as the atmosphere. It will be recognized that while the fuelmetering and discharge means 14 has only a single stage of amplificationand receives but one control input, it is merely illustrative of arudimentary fluidic fuel metering device of the type hereinbefore notedand of which more complete and complex forms are known. It should beevident that with more than one stage of amplification and additionalfuel return or vent passages, the inertial effects upon the fuel in thereturn system become more critical.

Referring now to FIGS. 1, 2, and 3 and particularly to FIG. 3, thepreferred embodiment of the present invention is illustrated. Theinsulating means 16 comprise an enclosure or body 100 having a partitionor weir 102 situated therein to form a reservoir 103. The body 100further includes a fluid inlet 104 arranged to discharge fluid into thereservoir 103 while a discharge passage 106 is arranged to exhaustfluid, in excess of the reservoir volume, from the enclosure 100. Thedischarge passage 106 is in communication with the return line 22 sothat the fluid discharged, which in a fuel system as illustrated in FIG.1 would be gasoline, would be returned to the fuel tank 10. The inlet todischarge passage 106 is shown as being sealed by floating ball 110.Other suitable means to prevent air from entering the return line wouldbe applicable. An air inlet 108 is arranged to maintain the pressurewithin the enclosure at the prevailing atmospheric or an ambientpressure depending upon the pressure desired by the system designer.

The fluid inlet 104 communicates the reservoir 103 with the fluidicelement vent passage means here illustrated by excess fluid outlet butwhich should be considered representative of the fluid vents and excessfluid passages within the fluidic computing portion of the system. Thefluid inlet is arranged to discharge all or substantially all, excessfluid into the reservoir. As will be observed, the reservoir has a pairof lateral dimensions and is oriented with the minor lateral dimensionbeing parallel to the direction of motion of the vehicle. This isindicated by the MOTION arrows in FIGS. 2 and 3.

Referring now to FIGS. 1, 4 and 5, and specifically to FIG. 4, analternative embodiment of the insulating means 16 is illustrated. Theinsulating means 16 comprises a body 200 forming a chamber having apartition of weir 202 located therein forming a reservoir 203. Theinsulating means 16 further includes a fluid inlet passage 204 and fluidexhaust passage 206 located on opposite sides of the weir or dam 202.The outlet passage 206 is connected, via return line 22 including checkvalve 24, to the fuel tank 10. The fluid inlet passage 204 is located soas to discharge fluid substantially into the center of the reservoir 203behind the weir 202 and is connected to the fuel vent and exhaustpassage system of the fuel metering and discharge means 14. The fluidinlet 204 would be connected to each fuel return and vent passage in afuel metering and discharge means 14 having more than one fluid logicelement. The insulating device 16 is also of utility in those systemsutilizing positive pressure, as opposed to the negative pressure venturidepression systems. The arrow labeled MOTION in FIG. 5 illustrates theorientation of the device with regard to the forward and reverse motionof a vehicle having forward and reverse motion parallel to the MOTIONarrow.

OPERATION OF THE PREFERRED EMBODIMENT In operation, fuel under pressurewould be provided by pumping means 12 to the fluid logic elementcalculating stage 26 of the fuel metering and discharge means 14.Sufficient fuel would have to be provided so that there would besufficient fuel available to satisfy the most extreme demands. Thiswould mean that under all other operating conditions, the fuel providedto the main or primary metering element 26 would be in excess of theexisting demand. The excess fuel would have to be returned to the fueltank. The insulating device 16 is interposed between the fuel meteringand discharge means 14, and fuel tank 10. The excess fuel iscommunicated through inlet passage 104 so as to fill the reservoir 103to form a substantially constant volume reservoir of excess fuel. Fueldischarged in excess of the reservoir volume will spill over thepartition or darn 102 where it will pass through the outlet passage 106to return to the fuel tank 10. The insulating device 16 may be placed inproximity to the fuel metering and discharge means 14 so that the totalvolume of fuel within the conduit communicating the fluid logic elementfluid vent to the reservoir is reduced. The insulating element 16 has amajor lateral dimension which is substantially greater than the minorlateral dimension. This aids in reducing the volume of the reservoir. Itis of particular advantage when the isolating device is oriented withthe minor lateral dimension substantially parallel to the direction ofvehicular motion, and hence the direction of the majority ofacceleration forces. In this orientation, attitude changes to the fuelsystem are less pronounced and the narrowness of the reservoir causesfuel depth at the outlet of the fluid inlet passage 104 to remainsubstantially constant for vehicle acceleration and deceleration.

The depth of the reservoir 103 would be readily controllable by varyingpartition height or by varying the vertical placement of the passage 104during fabrication of the isolating means 16 to provide a substantiallyconstant back pressure on the fluidic computing and discharge means onthe order of 1 to 2 inches of fuel. This substantially constant backpressure would permit the fuel system designers to virtually ignore theinertial force problems and to design the system to operate with aknown, substantially constant back pressure.

By placing the outlet of the fluid inlet passage 104 at the approximatehorizontal center of the reservoir 103, the changes in attitude of thevehicle will have slight effect on the static pressure head at theoutlet. Furthermore, since the most pronounced attitude changes areexperienced as a result of the vehicle negotiating a hill, the minorlateral dimension being parallel to such changes serves to furtherreduce the effect on the fuel return system.

It would also be possible to fabricate the fluid logic element orelements so that they could be located within the reservoir so that thelength of line between the elements and isolating device reservoir maybe further reduced.

I claim:

1. In a fuel system having a fluid element means to control fuel flow,the improvement comprising:

return means operative to divert excess fluid to the fluid supply; and

isolating means interposed in the return means downstream of the fluidelement means operative to substantially eliminate the influence of theinertial effects of the fluid in the return means on the fluid elementmeans.

2. The system as claimed in claim 1 wherein said isolating meanscomprise:

means for forming a reservoir in substantially constant pressurecommunication with the fluid return passage of the fluid logic device;and

means for returning fluid in excess of the reservoir volume to the fluidsupply.

3. The system as claimed in claim 1 wherein said isolating meanscomprise:

a chambered body having a fluid inlet means and a fluid exhaust means;

said fluid inlet means communicating with the fluid return passage ofthe fluid logic device via a first portion of the return means;

said fluid exhaust means communicating with the fluid supply via asecond portion of the return means;

a partition located in said chambered body operative to form a reservoirregion in the vicinity of said fluid inlet means; and

said reservoir operative to prevent direct fluid communication betweensaid fluid inlet means and said fluid exhaust means.

4. The system as claimed in claim 3 wherein said reservoir has a pair oflateral dimensions and said fluid inlet means includes an inlet portsubstantially at the middle of said pair of lateral dimensions.

5. The system as claimed in claim 4 wherein one of said lateraldimensions is substantially larger than said width dimension.

6. The system as claimed in claim 5 wherein the minor lateral dimensionis oriented to be substantially parallel to the direction of themajority of inertia forces exerted on the system.

7. The system as claimed in claim 4 wherein said inlet port is in aplane substantially parallel to the direction of the majority of inertiaforces exerted on the system. 8. The system as claimed in claim 3wherein said fluid inlet means includes a fluid inlet port arranged todischarge fluid into said reservoir thereby establishing a substantiallyconstant fluid back pressure for the fluid logic device metering means.

9. The system as claimed in claim 8 wherein said inlet port is arrangedto be substantially parallel to the direction of the majority of inertiaforces exerted on the system.

10. A fuel system for engines comprising: a source of fluid; pumpingmeans communicating with said source of fluid operative to provide apressurized fluid stream;

fluidic means for receiving said fluid stream and operative to produce afirst fluid flow controlling engine fuel;

return means for returning the portion of said fluid stream in excess ofsaid first fluid flow to the source of fluid; and

including insulating means operative to maintain a substantiallyconstant level of fluid pressure in said return means between saidfluidic means and insulating means.

11. In a fuel system having a fluidic amplifier means to control fuelflow, the improvement comprising:

return means having a fluid inlet at the fluidic amplifier meansoperative to divert excess fluid away from the fluidic amplifier means;and

means operatively associated with the return means to provide asubstantially constant fluid pressure at the return means fluid inlet.

References Cited UNITED STATES PATENTS 3,020,030 2/1962 Capehart 26l(S.P.) 3,372,912 3/1968 Benmore 26l-(S.P.) 3,386,710 6/1968 York, Jr.261-36.1 3,389,894 6/1968 Binder 26l36.l 3,406,951 10/1968 Marks 26136.13,413,994 12/1968 Sowers III l37-81.5 3,477,699 11/ 1969 Drayer 26 l36.l

TIM R. MILES, Primary Examiner US. Cl. X.R.

